fix: limit calls to SQL Admin API on startup

internal/proxy/proxy.go

@@ -122,7 +122,7 @@ type Config struct {
 	// CredentialsJSON is a JSON representation of the service account key.
 	CredentialsJSON string
 
-	// GcloudAuth set whether to use Gcloud's config helper to retrieve a
+	// GcloudAuth set whether to use gcloud's config helper to retrieve a
 	// token for authentication.
 	GcloudAuth bool
 
@@ -133,7 +133,7 @@ type Config struct {
 	// increments from this value.
 	Port int
 
-	// APIEndpointURL is the URL of the google cloud sql api. When left blank,
+	// APIEndpointURL is the URL of the Google Cloud SQL Admin API. When left blank,
 	// the proxy will use the main public api: https://sqladmin.googleapis.com/
 	APIEndpointURL string
 
@@ -204,7 +204,7 @@ type Config struct {
 	// Prometheus enables a Prometheus endpoint served at the address and
 	// port specified by HTTPAddress and HTTPPort.
 	Prometheus bool
-	// PrometheusNamespace configures the namespace underwhich metrics are written.
+	// PrometheusNamespace configures the namespace under which metrics are written.
 	PrometheusNamespace string
 
 	// HealthCheck enables a health check server. It's address and port are
@@ -479,18 +479,13 @@ func NewClient(ctx context.Context, d cloudsql.Dialer, l cloudsql.Logger, conf *
 
 	for _, inst := range conf.Instances {
 		// Initiate refresh operation and warm the cache.
-		go func(name string) { d.EngineVersion(ctx, name) }(inst.Name)
+		go func(name string) { _, _ = d.EngineVersion(ctx, name) }(inst.Name)
 	}
 
 	var mnts []*socketMount
 	pc := newPortConfig(conf.Port)
 	for _, inst := range conf.Instances {
-		version, err := d.EngineVersion(ctx, inst.Name)
-		if err != nil {
-			return nil, err
-		}
-
-		m, err := newSocketMount(ctx, conf, pc, inst, version)
+		m, err := c.newSocketMount(ctx, conf, pc, inst)
 		if err != nil {
 			for _, m := range mnts {
 				mErr := m.Close()
@@ -609,7 +604,7 @@ func (m MultiErr) Error() string {
 	return strings.Join(errs, ", ")
 }
 
-// Close triggers the proxyClient to shutdown.
+// Close triggers the proxyClient to shut down.
 func (c *Client) Close() error {
 	mnts := c.mnts
 
@@ -704,7 +699,7 @@ func (c *Client) serveSocketMount(_ context.Context, s *socketMount) error {
 			sConn, err := c.dialer.Dial(ctx, s.inst, s.dialOpts...)
 			if err != nil {
 				c.logger.Errorf("[%s] failed to connect to instance: %v", s.inst, err)
-				cConn.Close()
+				_ = cConn.Close()
 				return
 			}
 			c.proxyConn(s.inst, cConn, sConn)
@@ -719,7 +714,7 @@ type socketMount struct {
 	dialOpts []cloudsqlconn.DialOption
 }
 
-func newSocketMount(ctx context.Context, conf *Config, pc *portConfig, inst InstanceConnConfig, version string) (*socketMount, error) {
+func (c *Client) newSocketMount(ctx context.Context, conf *Config, pc *portConfig, inst InstanceConnConfig) (*socketMount, error) {
 	var (
 		// network is one of "tcp" or "unix"
 		network string
@@ -753,13 +748,24 @@ func newSocketMount(ctx context.Context, conf *Config, pc *portConfig, inst Inst
 		case conf.Port != 0:
 			np = pc.nextPort()
 		default:
+			version, err := c.dialer.EngineVersion(ctx, inst.Name)
+			if err != nil {
+				c.logger.Errorf("could not resolve version for %q: %v", inst.Name, err)
+				return nil, err
+			}
 			np = pc.nextDBPort(version)
 		}
 
 		address = net.JoinHostPort(a, fmt.Sprint(np))
 	} else {
 		network = "unix"
 
+		version, err := c.dialer.EngineVersion(ctx, inst.Name)
+		if err != nil {
+			c.logger.Errorf("could not resolve version for %q: %v", inst.Name, err)
+			return nil, err
+		}
+
 		address, err = newUnixSocketMount(inst, conf.UnixSocket, strings.HasPrefix(version, "POSTGRES"))
 		if err != nil {
 			return nil, err
@@ -771,7 +777,7 @@ func newSocketMount(ctx context.Context, conf *Config, pc *portConfig, inst Inst
 	if err != nil {
 		return nil, err
 	}
-	// Change file permisions to allow access for user, group, and other.
+	// Change file permissions to allow access for user, group, and other.
 	if network == "unix" {
 		// Best effort. If this call fails, group and other won't have write
 		// access.
@@ -785,7 +791,6 @@ func newSocketMount(ctx context.Context, conf *Config, pc *portConfig, inst Inst
 // newUnixSocketMount parses the configuration and returns the path to the unix
 // socket, or an error if that path is not valid.
 func newUnixSocketMount(inst InstanceConnConfig, unixSocketDir string, postgres bool) (string, error) {
-
 	var (
 		// the path to the unix socket
 		address string
@@ -831,7 +836,6 @@ func newUnixSocketMount(inst InstanceConnConfig, unixSocketDir string, postgres
 	}
 
 	return address, nil
-
 }
 
 func (s *socketMount) Addr() net.Addr {
@@ -842,7 +846,7 @@ func (s *socketMount) Accept() (net.Conn, error) {
 	return s.listener.Accept()
 }
 
-// close stops the mount from listening for any more connections
+// Close stops the mount from listening for any more connections
 func (s *socketMount) Close() error {
 	return s.listener.Close()
 }
@@ -853,8 +857,8 @@ func (c *Client) proxyConn(inst string, client, server net.Conn) {
 	var o sync.Once
 	cleanup := func(errDesc string, isErr bool) {
 		o.Do(func() {
-			client.Close()
-			server.Close()
+			_ = client.Close()
+			_ = server.Close()
 			if isErr {
 				c.logger.Errorf(errDesc)
 			} else {

internal/proxy/proxy_other.go

@@ -114,15 +114,9 @@ func (c *Client) Lookup(ctx context.Context, instance string, _ *fuse.EntryOut)
 		return l.symlink.EmbeddedInode(), fs.OK
 	}
 
-	version, err := c.dialer.EngineVersion(ctx, instance)
-	if err != nil {
-		c.logger.Errorf("could not resolve version for %q: %v", instance, err)
-		return nil, syscall.ENOENT
-	}
-
-	s, err := newSocketMount(
+	s, err := c.newSocketMount(
 		ctx, &Config{UnixSocket: c.fuseTempDir},
-		nil, InstanceConnConfig{Name: instance}, version,
+		nil, InstanceConnConfig{Name: instance},
 	)
 	if err != nil {
 		c.logger.Errorf("could not create socket for %q: %v", instance, err)